This invention relates generally to gas generation and, more particularly, to devices and methods for inflating an inflatable device such as an inflatable vehicle occupant restraint of a respective inflatable restraint system, for example.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an “airbag cushion,” that is inflated or expanded with gas such as when the vehicle encounters a sudden deceleration, such as in the event of a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, the cushion begins to be inflated in a matter of no more than a few milliseconds with gas produced or supplied by a device commonly referred to as an “inflator.”
Many types of inflator devices have been disclosed in the art for the inflating of one or more inflatable restraint system airbag cushions. Known forms or types of inflator devices include inflators known as “blowdown” inflators and “reverse flow” inflators. In a blowdown inflation system, a pyrotechnic or other selected material is commonly burned to create a build-up of pressure within a compressed gas storage chamber such as to result in the rupture or release of inflation gas therefrom when the internal pressure reaches a predetermined level or range. Thus, in blowdown inflator devices, the opening or rupture of a seal, burst disk or the like within the inflator typically results or produces a flow of heated or elevated temperature inflation gas from the device and into an associated airbag cushion. While blowdown inflation systems can desirably be of relatively lower cost and complexity, such systems can result in the delivery of inflation gas to an associated airbag cushion at a higher temperature, pressure and/or mass flow rate than may otherwise be required or desired.
In “reverse flow” inflator devices, an actuating initiator and openings wherethough the inflation gas exits from the inflator device are typically at or along the same end or side of the inflator device. Thus, in typical reverse flow inflators, the initial inflation gas exiting from the inflator device and passing into an associated airbag cushion is relatively cool and is later followed by heated or elevated temperature inflation gas. Consequently, reverse flow inflators which initially provide or supply a relatively cool inflation gas, followed by heated or elevated temperature inflation gas to an associated airbag cushion, can typically more easily provide or result in the more gradual deployment of the associated airbag cushion, as may be required or desired in particular deployment applications.
Specific types of prior art inflator devices include compressed stored gas inflators, pyrotechnic inflators and hybrid inflators. Unfortunately, each of these types of inflator devices has been subject to certain disadvantages such as one or more of having a greater than desired weight, requiring more than desired space or volume, producing undesired or nonpreferred combustion products in greater than desired amounts, and producing or emitting gases at a greater than desired temperature, for example.
Modern inflatable restraint system design, manufacture, production and operation has generally been moving in a direction towards or to relatively small, lightweight and economical modern vehicle components and assemblies. Commonly assigned, Rink, U.S. Pat. No. 5,669,629, issued Sep. 23, 1997; Rink et al., U.S. Pat. No. 5,884,938, issued 23 Mar. 1999; and Rink et al., U.S. Pat. No. 5,941,562, issued 24 Aug. 1999, each generally relates to apparatus for and methods of gas generation which at least in part rely on the decomposition or dissociation of a selected gas source material for gas generation. The disclosures of each these patent is hereby incorporated by reference herein and made a part hereof, including but not limited to those portions which specifically appear hereinafter.
In one form of such recently developed inflator device, inflation gas is produced or formed, at least in part, via the decomposition or dissociation of a selected gas source material, such as in the form of a compressed gas and such as via the input of heat from an associated heat source supply or device. Nitrous oxide is a preferred gas source material specifically disclosed in one or more of these patents. One or more of the above-identified patents disclose that such an apparatus for and method of gas generation can be helpful in one or more of the following respects: reduction or minimization of concerns regarding the handling of content materials; production of relatively low temperature, non-harmful inflation gases; reduction or minimization of size and space requirements and avoidance or minimization of the risks or dangers of the gas producing or forming materials undergoing degradation (thermal or otherwise) over time as the inflator awaits activation.
Nevertheless, further or continued improvements in inflator devices, such as relating to design, manufacture, production and/or operation, are desired.